Mar 02 2011

Cell Phones and Brain Function

I am a bit late to this news item but continue to get questions about it, so I thought I would cover it. A recent study shows that cell phone use is associated with alterations in brain metabolism. This may lend credibility to the claim that there are potential risks to cell phone use.

I was interviewed last week about this news item for NPR, and you can listen to the segment here.

Background

There is ongoing concern and controversy over whether or not there is any health risk from cell phone use. (I have written about this here, and here is another article on SBM about the topic.) Specifically there is a concern about an increased risk of brain tumor from cell phone use. The basic science largely does not support plausibility for a risk, given that the energy contained in the radiofrequency radiation from cell phones is too weak to break chemical bonds – and it therefore too weak to cause DNA mutations that might lead to cancer.

The epidemiological evidence is a bit mixed, but mostly negative. For adults there does not appear to be any increased risk of brain tumors for 10-15 years of cell phone use. There is less data with children. In addition there has not been a increase in brain tumors overall since the widespread use of cell phones over the last 10-20 years. There may, of course, be a delayed effect from long term use (longer than our current studies) – but only time will tell.

I conclude from all of this that there is probably no direct biological risk from cell phone use, or if there is any risk it is very small. But if you want to be on the safe side, limit your cell phone use, or use the speakerphone option so the phone is not up against your head. Parents may want to delay or limit their children’s use of cell phone until more data is in. I am not recommending these measures – just pointing out that if the current level of uncertainty is worrisome, these are the reasonable steps to take. Devices that claim to protect users from radiation do not work – there is no way to block the EM radiation without also interfering with the phone’s function. So if the phone works, you are getting exposure.

The Current Study

Into this mix comes the recent study, which shows, essentially, that cell phone use increased glucose metabolism on the side of the brain where a cell phone is being held and is turned on. The data (here is the full version of the study for those who have access to JAMA) are as follows:

Whole-brain metabolism did not differ between on and off conditions. In contrast, metabolism in the region closest to the antenna (orbitofrontal cortex and temporal pole) was significantly higher for on than off conditions (35.7 vs 33.3 μmol/100 g per minute; mean difference, 2.4 [95% confidence interval, 0.67-4.2]; P = .004). The increases were significantly correlated with the estimated electromagnetic field amplitudes both for absolute metabolism (R = 0.95, P < .001) and normalized metabolism (R = 0.89; P < .001).

There was a significant increase in glucose metabolism on the side of the cell phone use, but not for the whole brain in the on vs off condition. The PET scan images themselves do not look impressive to the naked eye – there appears to be similar activity in the right and left frontal lobes. But a statistical analysis of the raw data shows a difference. This could mean that we are seeing a statistically significant, if not biologically significant, effect.

But if we take the results at face value, what do they mean? The authors acknowledge, “This finding is of unknown clinical significance.” Basically, it may mean nothing.

There is a separate question as to the mechanism. It is possible that the increased metabolism is due to temperature increase. Most of the energy produced by the cell phone is converted into heat, which heats up the phone, the hand holding the phone, and the side of the head against which it is pressed. The authors conclude that temperature alone is not a likely explanation because of the distance involved, but I am not convinced this can be so easily dismissed. Perhaps the radiofrequency radiation is increasing the temperature in the tissue directly, and not just spreading from the outside. There may also be a separate mechanism by which metabolism is increased.

The big question is – what risk, if any, does this pose. There is no obvious risk to a little bit of increased metabolism. There is no particularly reason to this this would pose a health risk. The effects may, in fact, be beneficial. Some have already speculated that this could translate into a treatment for depression, for example.

Also – this study does not lend much plausibility to the notion that cell phone use can increase risk of cancer. The increase in metabolism does not plausibly lead to higher mutations or other damage that would lead to cancer. In the end this study does not affect the plausibility argument significantly.

Conclusion

The results of this study are certainly interesting and deserving of follow up research. The bigger question of the safety of cell phones, given their widespread and increasing use, also deserves further monitoring.

But this study does not mean that cell phones pose a health risk, and the effect seen does not even lend much plausibility to the possibility of risk. We are likely seeing a harmless nonspecific effect on cell metabolism.

Unfortunately, this study is easily used to stoke unwarranted fears about cell phone use.

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